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Subjects

Abstract

Isotopes of heavy elements are produced in various amounts by nuclear processes in stars1,2. Consequently, the presence of isotopic anomalies in the Solar System is considered to reflect the presence of presolar grains condensed in previous generations of stars3 and not a (proto-) Solar System process. However, for oxygen, the major rock-forming element, it has been shown that physico-chemical reactions applicable to the presolar cloud or the protoplanetary disk were a possible source of isotopic variations due to mass-independent isotopic fractionation (MIF)4,5. Here we show that MIF effects are not restricted to oxygen, but can also be produced for titanium. Titanium-rich grains experimentally condensed from a TiCl4(g)/C5H12(g) plasma exhibit MIF effects from −25% to +120% for all Ti isotopic ratios. These large Ti isotopic variations follow the model developed for oxygen MIF6 and mimic the Ti isotopic anomalies observed in some presolar grains. This effect is ascribed to the reactions between chemically indistinguishable isotopes6 and could contribute to the complexity of isotopic anomalies observed in Solar System materials1,7,8,9,10,11,12,13,14.

Contributions

F.R. designed the project and provided samples for this study. R.T. collected and analysed the NanoSIMS data. F.R., R.T., Z.D. and M.C. interpreted the cosmochemistry results and wrote the paper. G.L. interpreted the plasma physics results. B.D. and M.R. obtained and interpreted the microscopic images. P.R. participated in the interpretation of the Ti-MIF effects in terms of theoretical physics.